1. Field of the Invention
The present invention relates to a lithography simulation method, a mask pattern correction method, and a processed substrate topography correction method, more particularly, to a lithographic simulation technology for finding the distribution of light intensity on the surface of a substrate.
2. Description of Related Art
During lithographic processing of a semiconductor device, a portion of the light shone onto the surface of the substrate is sometimes blocked due to uneven portion such as step-like parts or other irregularities on the surface of the substrate. Conventional lithography simulations calculate the distribution of light intensity at the surface of the substrate using simple methods that assume the incident light and exiting light are normal to the surface of the substrate (Japanese Laid-Open Patent Publication No. 2002-6475), or using rigorous methods in which the light intensity distribution at the step-like part is calculated by solving Maxwell's equations.
The rigorous method is not preferred from a practical standpoint because the calculations require an enormous amount of time. Meanwhile, although the aforementioned simple method is able to achieve some degree of calculation precision when the shape of the step-like part is somewhat gentle, it has poor precision when there are more severe irregularities on the substrate. The poor calculation precision is thought to be caused by the fact that the orientation of light reflecting from step-like parts deviates from the normal direction, and it has been believed that the only way to improve the calculation precision is to use the aforementioned rigorous method.